Werner Institut für Theoretische Physik Leibniz Universität Hannover New directions in the Foundations of Physics Washington April 24 2015 Is an ontological commitment at the quantum level ID: 549072
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Slide1
Reinhard F. WernerInstitut für Theoretische PhysikLeibniz Universität Hannover
New directions in
the Foundations of Physics
WashingtonApril 24, 2015
Is an ontological commitment at the quantum level helpful for good physics?
Version
including
some
comments
by
Shelly GoldsteinSlide2
Introduction
(
introducing
myself)
mathematical
quantum physicistStatistical
Mechanics, recently mostly Q Informationstudent
of Günter LudwigSlide3
in the sense every scientist should be
I am a Realist
Build
theories/explanations that can clash
with experience/experimentAvoid lines of reasoning/investigation known to be
error prone
Appeal to authority/scripture,
free fantasy formalized
methodology
Don‘t
fool yourself (and others)
Check on your confirmation bias and premature
hypothesizingSlide4
I am a Realist
about
This
is naive but required for the enterprise of empirical sciencealways needs critical
evaluation
observational data
Other
claims to reality
Can only
be stated in the context of a theory
can
only
refer
to
theoretical
terms
crucially
depend
on
the
role
a
term
plays
in
the
theory
A
claim
is especially weak, when the term
depends
on
arbitrary
choices
(
eg
vector
potentials
)
Can
be
eliminated
without
change
of
empirical
contentSlide5
If claims to Reality depend on the role of a notionin the “best
theory about
the
subject“, what makes a “good theory“?
Example of a “bad theory“: quantum mechanics applied to 1024 particlesNeeds special situations and “approximations“,which must be
counted as part of a
theory (Stat. Mech)(Theory
Axioms “all conclusions thereof“)
empirical correctness
power of the formalism
to actually reach conclusions
manageable computational complexitySlide6
Introduction
(
introducing
myself)
mathematical
quantum physicistStatistical
Mechanics, recently mostly Q Informationstudent
of Günter LudwigI see
my job as Explaining
how QM works and what we can
expectClarifying conceptual issues
Increasing
the
strength
of
the
quantum
formalism
Increasing
the
expressive power
of
QM
Consolidating
reduction
relations
between
theories
and
modelsSlide7
Historical ExamplesSlide8
Earth around
Sun
Really
?
Sun
gives
better
inertial
frame
!
Coordinate
choice
. So
what
?Slide9
The Ether
Maxwell 1861
Mechanical
metamaterial
Continuous mediumwith funny propertiesdispensibleforgotten
It
matters
little whether the ether really
exists; that isthe
affair of the metaphysicians. The essential thing for
us is [...] that this hypothesis
is convenient for the ex-planation
of
phenomena
. After all,
have
we
any
other
reason
to
believe
in
the
existence
of
material
objects
?
[...]
no doubt, some
day
the ether will be thrown aside as useless. Poincaré 1888 (
cited after Darrigol)Slide10
Apfel
An apple’s trajectory
nowhere differentiable
2x
differentiable
Trajectory?
Continuity
and
Continuum
Slide11
How real are the reals?Like all mathematical objects they
are human inventions
(but mathematical
Platonism is beside the point here
)Could we not do Physical Geometry with all distancesrational constructible with ruler and compassreal hyper-real (non-standard analysis
)At any
finite accuracy these are indistinguishable
refinement process =
Hausdorff completion
unique
!
Idealization
patches
up
our
ignorance
of
small
scale
geometrySlide12
Quantum Mechanics
Although
quantum mechanics is hugely successful
practically, its interpretation is still a matter of debate. Bullshit
Legitimate question of any student:
Tell me what I need to
know (e.g., about interpretation) to participate in
that success story. Slide13
Quantum Mechanics
some
good news...
There is only one interpretationand there is consensus about this
This interpretation is local
Quantum
mechanics
has no measurement problemSlide14
There is only one interpretationand there is consensus about
this
Depends
on what you mean
by interpretation(a) A basic set of rules for connecting observations to elements of the mathematical formalism
agreement (e.g., Q Information community)
(b) “Spelling out an ontology
“ (Esfeld) Poetic
interpretation Natural Philosophy 19th century style
less
agreementSlide15
A basic set of rules for connecting observations to elements of the
mathematical formalism
Minimal
Statistical Interpretation
Operational Quantum
Mechanics
1000100101100110101001100101110101000100100100110
p
(
1
)
p
(
0
)
Theory
only
refers to such probabilities.
preparation
,
state
measurement
,
observable
F
, tr(
F
).
0Slide16
Quantum Mechanics is a probability theory without sample spaces
No
unique decomposition
into pure statesNo dispersion-free states
States (=“probability distributions“) are not distributions of “objective“ propertiesNo conditioning (in general)= a generalized probabilistic theory (GPT)=
convex state space approach (Ludwig 1960s)
ensemble interpretation (Einstein, von Neumann`26)Slide17
Remark
about
Probability:
Subjective
vs.
frequentist
“
Subjects“, rational agents etc are
constrained by rationality rules and Bayes
‘
rule
to
act
like
frequentists
For
frequentism
“
probability
“
is
a
theoretical
term
in a
theory
of
random
sources
Applicability of this theory never follows from observation
alone, but is partly a subjective decision
Difference
not
as
great
as
it
may
seem
,
especially
when
there
are
sufficient
data
Agreement on:
Probability
distributions
or
are
not
attributes
of
individual
systemsSlide18
The minimal interpretation is local
No operation on
one part of
a system makes a detectable difference on another part
, unless interaction is explicitly includedPrototype locality already assumed in the setup: Ludwig: Principle of directed
interactionNo backreaction
from measurement to preparation
Also
needed to
define “channels“operating on “unknown quantum
states“
x
Informational
turn:
Analyze
systems
in
terms
of
what
can
be
encoded
on
them
and
reliably
read
outSlide19
The shape
of
the state
space
=
key structural feature
of the system type in a generalized
probabilistic theory (GPL)A
theory is called classical iff
any
two
convex
decompositions
of
a
state
have
a
common
refinement
(
no
Schrödinger
steering
)
any
state
has
a unique decomposition
into
extreme
points
(
state
space
is
a “
simplex
“)
the
faces
of
its
state
space
form a distributive
lattice
(
Boolean
logic
)
any
two
observables
can
be
measured
jointly
there
is
“
finest
“ observable
,
from
which
all
others
can
be
simulated
by
post-
processing
Every observable
can
be
measured
without
disturbance
sample
spaceSlide20
You assume classicality, if you demand a description of individual systems in terms of
“real
factual situations“ (Maudlin, mail Apr. 16)
elements of reality (EPR)a variable (Bell 1964)This is a highly non-trivial step beyond the minimal interpretation.Slide21
Quantum mechanics has no measurement problem
However
, some textbook accounts
have an MP.Better do without:
Quantum Fundamentalisminstead: QT does not apply directly to Macroscopic Bodies need StatMech for emergence of Classicality
Projection
Postulate & “Dual Evolution“
instead: general “instruments“ measuring
filtering for “properties“
Fixed “
objective“ results are
the starting point. A “
measurement
problem
“
arises
only
as
a
consistency
problem
:
Checking
that
fixed
results
are
consistent
with
the
Quantum Statistical
Mechanics treatment of devices. Slide22
Bell‘s Theorem*
*
Maybe not what
he thought he proved, but what
we learned from him. A theory cannot have all
three of the
following features
Correlation
Experiments explained
Classical Description Joint measurability
Hidden variables
Counterfactual
definiteness
“
Realism
“ ...
Locality
No Bell‘s telephone
Relativistic causalitySlide23
Bell‘s Theorem
One
can
prove this in the form:
Correlation Experiments violating CHSH Classical Description
Joint measurability
of Bob‘s
measurements
Violation
of Locality
Signalling just on
correlationsSlide24
In Operational Quantum MechanicsCorrelation
experiments
ok
Locality
No Bell‘s telephone Relativistic causality
ClassicalDescriptionSlide25
Bell‘s Theorem
(
Bohmian
Style)
Correlation Experiments with CHSH outcomesNonlocality
of Nature herself
(no theory
required)
There
is NO ASSUMPTION HERE“Real factual
situation“ is taken for granted as
feature
of
any
theory
. Slide26
Choose
!
will
you
take Classicalityand try to save the world
you
used to
know
or will
you take
Locality
and enter the
world
of
matrix
mechanics
So
let
us
play
a
bit
with
the
Blue
PillSlide27
Bohmian
Mechanics
I will
only
refer to the Goldstein et al version (ignoring
differences to
David Bohm‘s version
)
My encounters
:
Friends doing Nelson‘s
stochastic mechanics (
early
80s)
Paper (1986) on
generalizations
Various
rounds
with
Detlef Dürr
Paper on multi-time
correlations
Quantum
theory
without
observers
III
Clash
via
blog
(April 2013)
Comment on Tim
Maudlin‘s
“
What
Bell
did
“.
Last
summer
: Long email
exchange
on a
detector
problemSlide28
A theory must be about something
Note: “QM is about
atomic scale physics“
seems to count for nothing
Bohmian criticism of QMSlide29
A theory must be about some thing
Bohmian
criticism of QM
Note: “QM is about atomic
scale physics“ seems to count for no thingSlide30
A theory must be about some thing
The
solution: Thingify all
you can! Bohmian criticism
of QMQSlide31
Bohmian Mechanics
This will
then
remain true for all times ( “Quantum equilibrium
“)Slide32
Bohmians are not alone in
committing this category
mistake
Einstein attacked this as the “orthodox view“
of the wave function from 1927-1955One of the agendas of the EPR paper is to attack this (I think
successfully)Effectively this
is a spooky variable theory
And responsible for a good deal of the
supposed “non-locality“ of QM. Slide33
Ensemble Interpretation
Individual State Interpretation
puts
here
puts here
Operational
quantum
mechanics
/minimal int.systematizes theoretical and experimental practice“
incomplete“ and not ashamed of that
“orthodox“ view plain category
mistake
still
held
by
many
I
II
Einstein @ Solvay 1927Slide34
QHeisenberg told you that
you cannot
have trajectories. Here
they are! Cool!
Why are the situations and so different?Shouldn‘t each particle see just one hole?
Unsatisfying
explanation
:
You
have
to
compute
different
s.
Shut
up
and do it.
Bohmian
explanation
:
You
have
to
compute
different
s.
Do
it
and
then
solve
the
guiding
eq
. ( different
patterns
).
Now
shut
up
.
Ok. Sorry.
That
was
asking
too
much
.Slide35
QBM must share a grain
of
truth with QM,
because t(x)=|t(x)|2 for all t
This is easy to getNo compelling arguments
either way
Can
add any velocity
term v with div(v)=0Can
also add a diffusion term (Nelson), any diffusion
constant Can replace Q by any
abelian subalgebra (also finite dimensional/discrete/
momentum
, RFW
, `86
)
Can
let
mixed
states
do
the
driving
Meet
the
Bohmian
Demon
,
the
only
spectator
of
Bohmian Reality
Meet
Nelson‘s
Demon
,
the
only
spectator
of
StochMech
Reality
They
rarely
agreeSlide36
QBM must share a grain
of
truth with QM,
because t(x)=|t(x)|2 for all t
This is easy to getand also
wrong just around the corner
(arXiv:0912.3740
) Take two entangled, non-interacting particles
. Then two-time correlation
functions make sense in both BM and QMBut they
are quite different: eg QM: CHSH=2
2, BM: CHSH2No
special
link Q
BM
Q
QM
Bohmian
Answer
(
arXiv:1408.1651):
Have
to
describe
Q-
measurement
as
a
Bohmian
process
Collapse
by
the first measurement. Slide37
QBM must share a grain
of
truth with QM,
because t(x)=|t(x)|2 for all tSlide38
QBM is empirically
equivalent to
QM, because t
(x)=|t(x)|2 for all t
All the other quantum degrees of freedom?They just are
not real. Have to describe
entire experiment in BM language.Then
since ultimately every
measurement ends in position
dofempirical equivalence is reestablished
.
This preference for position is entirely ad hoc
Why
not
momentum
measurements
on
photons
(Jürg Fröhlich)?
Do
we
want
to
treat
“
result
in
pixel
on
screen
“ and “
result
in
ink
on
paper
“
as ontologically different?Microscopically
, we routinely transfer quantum
states
between
different
degrees
of
freedom
.
Need
Bohmian
Theory
of
ExperimentsSlide39
Bohmian
Theory
of Experiments I
Describe the whole
experimental arrangementin Bohmian terms.
Allows to claim a definite
outcome, because the particles of
the pointer hand are assigned
some QBM.
The End
This will
tell
us
nothing
about
the
empirical
relevance
of
the
microscopic
Bohmian
trajectories
:
All
interaction
via
.
No
known correlation between particle and
detector QBMSlide40
Bohmian
Theory
of Experiments I
Correlation between
particle and detector ?
45
pages
of
email
correspondence
(
summer
2014),
mainly
with
Shelly (
inconclusive
). Slide41
Summary:
Bohmian
Theory
(micro
)
Strictly
for the
Bohmian demonelse
could condition on his observations
threreby get signallingsubsystems
out of Q equilibrium
Dependent
on
arbitrary
choices
(Nelson,...)
Usually
at
odds
with
physical
intuition
&
oddly
biased
towards
position
vs.
other
physics
Shelly
to
me
(Bielefeld`13)
You
as
an
operationalist
should
not
complain
about
our
not
taking
spin
seriously
: For
you
nothing
is
real.
Me
(
now
):
Why
not
be
an
atheist
about
just
one
more
?Slide42
Bohmian
Theory
of Experiments II
Use strong assumptions
about the form of after the
experiment: No
need to follow the trajectories
.
System
Apparatus
with
macroscopically
distinct
and
with
forever
disjoint
configuration
support
These
are
mostly
copied
from
the
formal
theory
of
measurement
(von Neumann, Busch/Lahti/
Mittelstaedt
...)
When
transition
is
by
a fast
unitary
:
get
collapse
ariXiv
:
quant-ph
/0308038Slide43
Bohmian
Theory
of Experiments II
7: Genuine Measurements
ariXiv: quant-ph/0308038
Necessary condition for measurability of a random
variable: outcome probability distribution=
sesquilinear in “... neither
the velocity nor the
wave function [nor any multitime trajectory
property
]
is
measurable
“
Empirically
accessible
part
of
Bohmian
Me
c
hanics
Operational Quantum
Mechanics
=Slide44
A
Bohmian
piece
of
False
Advertising
Goldstein (Stanford Encyclopedia 2013):“In
fact, quite recently Kocsis et al. (2011) have used weak measurements to reconstruct the trajectories for single photons “as they undergo two-slit interference,” finding
“those predicted in the Bohm-de Broglie interpretation of quantum mechanics.”
Dürr&Lazarovici (Esfeld volume
, 2013):“There is, however, the possibility, using ”weak measurements” [...] to reconstruct experimentally the trajectories of the particles. Just recently this was achieved for the famous
double-
slit
experiment
.“ Slide45
The
Bohmian
micro
/macro
divide
For
small
systems, Qmust be hidden, lest we
can createquantum nonequilibrium
signalling
All for
only
On
measuring
instruments
the
Q-
configuration
is
identified
with
the
observed
outcomes
Demanding
additional
assumptions
on formal
measurement
theory:
forever disjoint supports of
branches
purity
of
branchesSlide46
Bohmian
Achievements
Solution
of the FNPP Measurement Problem given strong solution of FAPP MP
Derivation of operational QM: QM “
Trajectories“ QM
Clear
notion of arrival
times but must be avoided to
remain consistent
Existence
proof
for Hidden Variables
by
convincing
demonstration
why
not
to
use
them
Restoration
of
microscopic
Reality
for
the
eyes
of
the
Bohmian DemonSlide47
Two active Bohmians, Shelly Goldstein and Travis Norsen, were present at the talk, and we naturally
discussed some of
the issues in the
next available break. I asked Shelly to send me
some comments for inclusion in the posted version of the slides. These can now be found beginning on the next page.One participant
asked for the reference mentioned on
slide 35. It is RFW: “A generalization of stochastic mechanics and its relation to quantum mechanics”.
Phys. Rev. D 34(1986) 463-469.Ruth
Kastner complained about the “Bullshit” on slide 12, as not doing justice to the serious work that is actually being done on the issue of interpretation. She is right, of course. What I was mainly objecting to is that line about the unsettled interpretation being used as part of the general mystification of QM.
Notes added after the
workshop Slide 25 refers
to a debate I had with the
Bohmian
camp last
year
. The
editors
of
a
special
JPhysA
special
issue
celebrating
50
years
of
Bell‘s
inequalities
(
freely
available at http://iopscience.iop.org/1751-8121/47/42 )
had
asked me to comment on a contribution “What Bell did“ by Tim Maudlin (
see arXiv:14081826)because it was quite polemical
and
quite
against
the
mainstream
view
on
the
topic
. Tim was just
echoing
the
usual
Bohmian
line
(
see
also
the
Scholarpedia
article
(http://iopscience.iop.org/1751-8121/47/42
)
by
Shelly et al.
My
comment
(
see
the
special
issue
)
received
a
countercomment
by
Tim (arXiv:1408.1828),
showing
that
I
had
utterly
failed
to
get
through
to
him
(
see
also arXiv:1411.2120).
Probably
it
is
a matter
of
stating
the
assumption
in
words
Bohmians
recognize
.
At
the
workshop
Travis
at
least
agreed
to
the
statement
that
Bohmians
like
to
think
of
a
theory
as
something
involving
some
“
complete
description
of
the
real
factual
situation
independently
of
what
measuring
devices
we
choose
to
employ
“.
Only
you
should
perhaps
not
talk
of
a “
description
“
because
it
is
Nature
herself
, which
has that real factual situation. Since QM clearly
does not
work that way, and I somehow lack that direct access to the ‘Ding an sich‘, I still call that an assumption. Slide48
[Measurement problem]: I probably basically agree with that---though I
don't remember
what is
meant by FNPP. In any
case, quantum mechanics as you understand it does not have a measurement problem as usually
understood in the foundations
of quantum mechanics,
the problem of how
typical quantum measurements
can end up having
results (a pointer pointing
this way or that
way
, etc
.)
if
the
wave
function
of
the
system--
apparatus
composite
is
a
complete
description
of
that
system. Neither for you
nor for Bohmian mechanics
does
this
particular
problem
arrive
,
because
the
wave
function
is
most
definitely
not a
complete
description
of
the
relevant
system
.
One
important
difference
between
us
here
is
that
for
you
the
wave
function
is
not
really
an
objective
element
of
the
system
at
all, but just a
computational
device
,
whereas
for
Bohmian
mechanics
the
wave
function
must
be
taken
more
seriously
.
We
would
presumably
disagree
about
whether
that
is
a
virtue
or
a
vice
.
[FNPP was an
abbreviation
of
“for
no
practical
purpose
“]
Comments
by
Shelly Goldstein
,
mostly
on
the
last
slide
(
replies
and
further
comments
from
me
in [...])Slide49
[QM ∧ “Trajectories“⇒ QM] By “Trajectories“ here you of course
mean
the guiding
equation of Bohmian mechanics
, the additional equation with which BM supplements Schroedinger's equation. That's fine. But you're not
properly expressing here the
derivation. What is
important is this: On
the left only a
part of QM
is relevant, namely Schroedinger's
equation itself. And on the right
it
is
a different
part
of
quantum
mechanics
that
is
relevant,
namely
the
quantum
measurement
formalism
involving
Born
probabilities, operators as
observables, POVM's, etc. Those
things
are
certainly
not
part
of
the
formulation
of
Bohmian
mechanics
.
They
are
simply
what
emerge
as
a
convenient
means
of
description
when
Bohmian
mechanics
is
applied
to
an
analysis
of
results
of
experiments
.
[I
accept
that
.
But
what
was
the
achievement
,
really
?
It
only
shows
that
if
you
apply
the
raw
quantum
formalism
to
an
indirect
measurement
,
it
practically
does
not matter
how
you
describe
the
readout
at
the
macroscopic
level
.
Even
Bohmian
position
will do, but
only
if
you
make
sufficiently
strong
assumptions
guaranteeing
that
the
devices
live
up
to
macroscopic
expectations
.
You
see
that
this
fails
right
away
if
you
dare
to
move
a
Heisenberg
cut
in
one of the
earlier
stages
of
a
measurement
(A
perfectly
standard
thing
in QM for
getting
a
more
detailed
analysis
of
some
measurement
.) ]Slide50
[Arrival times] I wouldn't say that they must be avoided
. Rather one
must simply
be careful. In some situations
the Bohmian arrival times correspond precisely to the quantum probability current and provide a
principled explanation of
why the current
provides the relevant answer. But in
other situations it
is not the Bohmian
arrivals that are
reflected in the measurement results
.
There
is
nothing
terribly
mysterious
about
this
.
One
has
to
be
sure
the
experimental
arrangement
is such that the
arrivals becomes suitably
correlated
with
the
appropriate
apparatus
variables. In
Bohmian
mechanics
all
the
relevant variables
are
well
defined
,
but
one
must check
that
the
interactions
establish
the
appropriate
correlations
between
them
.
[I
should
comment
on
this
,
because
it
is
a residual
reference
to
a
section
that
I
deleted
from
the
talk
for lack
of
time.
Indeed
, in
the
80s I
wrote
a
couple
of
papers
on QM
arrival
time. I
did
feel
it
annoying
that
the
time
of
detector
clicks
are
routinely
recorded
in
the
lab, but
textbooks
were
mostly
silent
on
how
to
set
up
the
observables for
that
. (See
my
papers
http
://www.itp.uni-hannover.de/~
werner/WernerByTopic.html#j14)
The
Bohmian
or
Nelsonian
approach
has
obvious
first
hitting
distributions
, but
these
do
nothing
to
alleviate
the
problem
,
since
they
cannot
be
what
we
get
from
an
actual
detector (Trajectory properties are
not
measurable
). The
Bohmian
works
on
this
and
Shelly‘s
answer
make
the
point
that
sometimes
the
Bohmian
arrival
distribution
is
sort
of
ok, and
maybe
not
totally
off.
Having
worked
on
this
, and in
particular
on
finding
better
alternatives
than
the
probability
current
, I find
it
sad
that
Shelly‘s
answer
takes
that
current
(
which
is
quadratic
in
,
hence
“
measurable
“)
as
the
relevant
answer
.
] Slide51
[The eyes of the Bohmian Demon]A crucial element in establishing the
empirical
equivalence between BM
and orthodox quantum theory is
the proof that a Bohmian demon is not possible in a typical Bohmian universe: the sort
of system that such a
demon would have
to be is no
more possible that
a perpetual motion machine
. So the restoration of
microscopic reality is not for the
Bohmian
demon
.
Rather
its
point
is
this
:
Microscopic
reality
is
the
basis
of
macroscopic
reality. And in Bohmian mechanics
the behavior of the
fundamental
micro
-reality
yields
the
observed
behavior
of
the
macro
-reality on
the
basis
of
which
we
believe
in
quantum
mechanics
to
begin
with
.
Where
we
differ
here
is
this
: I
insist
that
measurement
and
observation
are
not fundamental, and
should
not
be
mentioned
in
the
formulation
of
a fundamental
physical
theory
. I
insist
, in
other
words
, on a
quantum
theory
without
observers
.
You
do not.
You
take
a
more
practical
stance
towards
physical
theory
.
Therefore
I
have
a
much
greater
need
for
micro
-reality.
Without
it
one
has
real
difficulty
in
insisting
on a
quantum
theory
without
observers
.
[I
agree
to
this
description
of
our
disagreement
]Slide52
[Existence proof for Hidden Variables by convincing demonstration why not to use them]Naturally
enough, I would express
that a bit
differently. Bohmian mechanics demonstrates
that despite all the no-hidden-variables arguments claiming to establish the impossibility of
hidden variables in quantum mechanics,
what Bohmian mechanics shows
is this: in order
to overcome these
argument one need
only invoke the
obvious ontology (that is
,
one
requiring
little
imagination
)---
namely
of
particles
,
described
by
their
positions
---
evolving
in
the
obvious
way, namely according to
the guiding equation
,
which
one
could
hardly
fail
to
find, in a
great
variety
of
ways
,
as
soon
as
one
bothers
to
look
for it.
From
this
OOEOW
the
quantum
formalism
,
probabilities
and all
the
rest
,
follows
.
[I
couldn‘t
make
sense
of
OOEOW.
And
probabilities
are
clearly
among
the
inputs
to
the
theory
,
as
the
initial
deed
of
the
demon
or
God
or
whoever
,
of
establishing
quantum
equilibrium
.
]Slide53
[The Bohmian micro/macro divide: slide 45]This makes it sound
as if
one *stipuates
* that for small systems Q is
hidden (in order to avoid some undesirable features). But this not so. One does not stipulate any such
thing. Rather, it
simply turns out that when
one analyzes BM one
finds that the
sorts of correlations
that typically can
arise in a Bohmian universe are
incompatible
with
the
sort
of
knowledge
that
would
allow
for
signalliing
,
or
for
violation
of
the
uncertainy principle or quantum
probability formulas.
What
you've
written
also
makes
it
sound
as
if
there
is
a genuine
conflict
between
what
is
true
for
micro
and
what
is
true
for
macro
.
There
isn't
.
Both
for
micro
and for
macro
(e.g.,
measuring
instruments
)
one
can
not
know
the
configuration
of
a
system
in
more
detail
that
its
Born
rule
probability
distribution
,
arising
from
its
wave
function
,
would
allow
. For
the
microrealm
this
is
a strong
limitation
. For
the
macrorealm
,
it's
not
much
of
a
limitation
at
all---
because
macro-masses
are
so
very
large (and
because
mechanisms
of
decoherence
are
so
pervasive
).
[Fair
enough
: The
trajectories
are
irrelevant in
the
microcase
and
superfluous
at
the
macro
-level. The
reason
I bring
this
up
is
the
tension
I
see
between
the
proved
invisibility
of
the
micro-trajectories
and
their
supposed
obviousness
at
the
macro
-level,
when
they
are
used
as
reality-
givers
for
the
measurement
results
. An
example
of
invoking
such “
obvious
relevance
“ was
given
by
Tim in
our
recent
email
exchange
,
asking
me
to
consider
the
kind
of
theoretical
prediction
that there is a large collection of particles with the shape of a cat moving in stereotypically cat motions, and the theory also (although this is less important) validates lot's of claims about how this collection would move if, say, a dog-shaped collection of particles came charging at
it...
In Washington
you
mentioned
the
paper
on
the
“Origin
of
absolute
uncertainty
“
as
the
place
where
your
above
Born
rule
argument
is
made
.
I‘ll
look
at
that
again
, but I am not
convinced
that
this
will
resolve
the
tension
.]